March 2008 Edition

aerospace manufacturing

Hypersonic aero builders reach for every advantage

From the standpoint of machine designers, builders, and end-users, the aerospace market seems to be moving at a hypersonic pace. With demand for military as well as commercial aircraft continuing to grow, the demand for speed to market is pushing not only the machine tool companies themselves but also such allies as Siemens Energy & Automation Inc.

"I've never seen it before," says Tim Shafer, Siemens director of aerospace. "I've been in and around the industry for years, and I've never seen the commercial and defense aerospace airframe segments hitting stride at the same time. And I'm talking in terms of just airframe components right now. If you go over to the jet engine side, they're going through a very similar challenge. Remember, for every airplane that you build there's at least one engine, and usually two engines, that go along with it. That capacity, with blisks and so forth, is highly reliant on five-axis machining."

In turn, today's machining community — in effect, a global network building parts for everything from F-35s and Boeing jetliners — looks to a company such as Siemens for an arsenal of technological advancements. Siemens has gladly obliged with such products as SINUMERIK 840D CNC as well as with what the company calls "advanced services," including:

• Virtual Production, through which virtual machining and optimization during simulation replaces any repeated test machining of the workpiece on a machine. As the automation solutions company boasts, "using in-house-developed simulation software, optimization is possible even in the preparatory phase of production."
• Mechatronic Support, which plays on the company's promise to customers to be "faster to the machine, faster on the market." For Siemens, this means going beyond mechatronic products and systems; it is pushing a service envelope "by configuring, developing, and testing the mechanical, electronic, and computer science components in interdisciplinary teams."
• EPS Condition Monitoring, with Web-based services that record plant status and allow for predictive maintenance.
• In today's aero market, every advantage is critical. As Shafer notes, "What I see in the aerospace market is robust growth in five-axis machining and composite technologies for the next two or three years."

Hitting stride

New materials, from titanium to aluminum alloys, are part of the aerospace manufacturing scene, creating new cutting, tooling, and workholding challenges. Moreover, the demand for finished products that can drill holes in the sky is putting pressure on almost every machine tool builder, according to Shafer.

"The discussion that I've had with the primes and in the supply chain is that there is a great concern about the supply chain capacity to machine five-axis parts," Shafer tells Tooling & Production. "And I've heard estimates of more than 1,000 five-axis machines being added to the capacity to make the rates that are being driven by new programs such as 787 and F-35 over the next three to five years.

"Obviously," he adds, "there's this tremendous upturn in business, with all these programs hitting stride at about the same time. And then there's Airbus and Boeing talking about a tremendous increase in single-aisle planes. The 737 has the largest backlog in history and with the A320 and A319, there's substantial Airbus work.

"Another thing — I was recently with aerospace companies in Winnipeg — the delivery for five-axis machines has really started to extend out over two years, and it has been quite a long time since machine deliveries that have extended beyond two years in the machine tool market. That indicates the capacity constraints of the machine tool builders."

The traditional five-axis builders are in the United States., Germany, Italy, and Japan. "And when you get to the blades," Shafer says, "Switzerland has machine builders that specialize in high-contour cutting machines." But Shafer admits that there's a chance builders could get "overrun." He says the aerospace industry may find "builders that are not really experts in five-axis machines selling five-axis machines because customers can get them faster from these builders."

"When you look at machine tool capacity in terms of building machines," he says, "there has been a massive consolidation of companies, and the overall capacity to build machines has been greatly reduced."

So are other players coming in? "Yes, certainly," he replies. "And that's why I say there's going to be machine builders that traditionally haven't built big five-axis machines that will jump on the opportunity to compete with traditional five-axis builders."

Analyzing advantage

Though Shafer can't predict what kind of performance builders just entering the market will be able to achieve, he does say that a service such as Mechatronic Support "is actually something that will enable the machine builder trying to enter that market, helping them to be more engineering savvy to help machines attain the right performance."

"Mechatronics, in its highest form, is a service that is provided by Siemens to machine builders and designers that allows them to come up with a robust design that is cost-effective — meaning that it is not over-designed or under-designed," Shafer explains.

"I mean you could use the ‘brute force' design methodology and make the machine really big and really heavy," he continues. "The negative impact of that is that it drives more cost in both the servos and the mechanics of the machine. The other side of that is under-designing the machine with cheap mechanics, and then you wind up with underperformance of the machine in terms of specifications.

This support, he says, "reduces the risk of redesign after the machine is actually built. It allows Siemens to actually predict the performance of the machine — accuracy, acceleration deceleration, and so forth — long before you build the machine. Without this kind of service, you'd have to build the machine and then test it out and find that you're not achieving the desired performance. Mechatronic Support reduces that risk of having to do redesigns after the machine is built."

As far as how it works, he says, "it's very traditional that a designer will do analysis of his design through finite element analysis — a mechanical analysis of the dynamics of the machine. What's missing in that analysis is the dynamics of the CNC controls and the servo drives. For example, if you're trying to design a 1G acceleration machine, there are certain mechanics you have to have in place, but there's also a control dynamic that is required to help achieve that without triggering a resonant vibration in the machine. Using Mechatronics, we can look at the mechanical model coupled with a virtual CNC motors and drives and we can adjust parameters inside this virtual control and inside this virtual drive to optimize the performance and to predict if there might be frequencies that cause oscillations. If we can't get those oscillations in the drive and control tuning, we go to the mechanical design and possibly add mass here or take mass out there."

Thus, he says, when you get the machine, you get a machine that meets the performance the original design intended. And, naturally, shorter development times — that is, time to market — result.

Cutting edge

Beyond that support, Siemens' assisting of customers to succeed in the aero market means working within the common control technology found in the aerospace version of the SINUMERIK 840D CNC and the compatible SIMODRIVE 611D motor and drive packages.

As the company notes, unique among the features of the package "are the ability to have the control calculate the complex five-axis transformations in real time versus relying on the upstream post processor." Again, the overall benefit is seen in reduced part setup time. "This achievement," according to Siemens, "is achieved by the use of the onboard TRAORI transformation orientation, a high-level language for kinematic machine transformation, as well as the Virtual NC Kernel package, a verification software which prevents any deviation in machining from the simulation modeling."

"As far as I know," Shafer says, "Siemens was the first one to come out with internal kinematic transformation, real-time transformation. Our kernel has the power to take all those calculations that used to take place in the post processor and that have been moved over into the CNC. So instead of having all those calculations take place offline, they now happen real time."

Even though the end products represent the world's most sophisticated aircraft, the machining process is first concerned with cutting parts. Tim Shafer understands that well.

"With transformation in the control," he says, "all you have to do is put that part somewhere on the work envelope, then you probe to find where the part physically is, and then you can translate and rotate the work-coordinate system to line up with the part. Then you can cut the part."

Siemens Energy & Automation

What do you think?
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